Nuclear particle accelerators, such as the Neutral Particle Beam (NPB) and Free Electron Laser (FEL) utilize large electrostatic or time varying electromagnetic fields to transfer energy from the electromagnetic field to particle velocity. Size constraints for orbital weapons platforms, considered with the high particle velocities required, drive designers to utilize large gradient electromagnetic fields in the accelerating structures. These large field gradients sometimes lead to electric field breakdown and resulting arc discharges between accelerator components. In order to minimize damage to the accelerator structure resulting from such discharges, it is desirable to detect and extinguish the discharge as soon as possible after it begins.
Present accelerators accomplish arc detection by sensing the optical emissions (ultraviolet or infrared) from the arc, by detecting anomalies in the amount of rf (radio frequency) power reflected by the accelerating structure, or by detecting surges in the rf amplifier electrical power. Each of these methods has disadvantages. Optical detectors must be placed inside the accelerating cavity and may not be within line of sight of the arc. Reflected rf power anomalies unrelated to arc discharges are common in particle accelerators so careful attention must be given to the problem of classifying the anomalies to ensure reliable arc recognition. Sensing surges in the rf amplifier prime power introduces delay proportional to the amount of energy storage (capacitance) designed into the power supply.
A technique for recognizing particle accelerator cavity arcs which does not require optical detectors would be advantageous. Since the optical detectors function by measuring optical emissions (ultraviolet or infrared) from the arc, the optical detectors must be placed within the accelerating cavity; however, a restriction for this type arc detection is a requirement that the optical detectors may not be within the line of sight of the arc. If the optical arc detector is not within the line of sight, an arc may be taking place, but the arc is not detected.
An object of this invention is to provide a detection system for particle accelerator cavity arcs based on a recognition of the electromagnetic spectrum of arc discharges.
Specifically, another object of this invention is to provide a detection system for particle accelerator cavity arcs at the time the arc begins to form.